1. Field to of the Invention
The present invention relates to a saddle riding or saddle riding type vehicle having an engine mounted at the center of the vehicle body frame and a saddle seat provided above the engine.
2. Description of Background Art
FIG. 8 is a side view of the saddle riding type vehicle of the related art, wherein the saddle riding type vehicle 100 mainly comprises a vehicle body frame 101, an engine 102 mounted at the center of the vehicle body frame 101, a saddle seat 103 provided above the engine 102, a fuel tank 104 disposed forwardly of the saddle seat 103, and front wheels 106, 106 (106 on the far side is not shown) rotatably mounted on the sides of the front portion of the vehicle body frame 101 via suspension mechanisms 105, 105 (105 on the far side is not shown). Further included are a steering 107 for steering the front wheels 105, 105, rear wheels 109, 109 (109 on the far side is not shown) rotatably mounted on both sides of the rear portion of the vehicle body frame 101 via suspension mechanisms 108, 108 (108 on the far side is not shown), a front propeller shaft 112 for transmitting rotary power of the engine 102 to a final speed reducer 111 on the side of the front wheels 106, 106, and a rear propeller shaft 114 for transmitting rotary power of the engine 102 to a final speed reducer 113 on the side of the rear wheels 109, 109.
The saddle riding type wheel 100 also comprises a propeller shaft 114 connected between the engine 102 and the final speed reducer 113 on the side of the rear wheel 109 with a falling gradient and an engine 102 disposed at the high position of the vehicle. Therefore, it is desirable to lower the center of gravity of the vehicle by disposing the engine 102 at the lower position.
On the other hand, since the final speed reducer 113 is disposed at the lower position, the height of the final speed reducer 113 from the ground decreases. As a consequence, it is difficult to ensure sufficient suspension stroke of the rear wheel 109. The term “suspension stroke” means the distance of movement of the wheel from a state in which the wheel is pushed up and the suspension is compressed to the maximum extent to a state in which the suspension is expanded to the maximum extent.
FIG. 9 is a plan view of the saddle riding type vehicle of the related art, and it is preferable that the saddle riding type vehicle 100 comprises a rear propeller shaft 114 being disposed from the engine 102 toward the final speed reducer 113 in almost parallel with the centerline of the vehicle body C and the final speed reducer 113 is disposed at the position closer to the left rear wheel 109.
When the rear final speed reducer 113 is disposed closer to the left rear wheel 109, the left drive shaft 115L is shorter than the right drive shaft 115R, and thus it is difficult to ensure a sufficient amount of movement of the wheel in the vertical direction. As a consequence, the suspension stroke of the rear wheels 109, 109 is limited.
Therefore, the inventor sought further enlightenments and proposed patent application Ser. No. 373986/2000 entitled “A SADDLE RIDING TYPE VEHICLE” as an improved technology relating to saddle riding type vehicles of the related art. The principal portions of this technology will be described in conjunction with FIG. 10 and FIG. 11.
FIG. 10 is a side view showing the layout of the propeller shaft of the saddle riding type vehicle proposed in the proceeding application, in which the saddle riding type vehicle 120 comprises a propeller shaft 134 connected to the engine 122 side via a coupling 136 at one end and to the final speed reducer 133 via a coupling 137 at the other end, and disposed in substantially parallel to the ground. As a consequence, the engine 122 could be disposed at the lower position, and thus the center of gravity could be lowered.
By arranging the propeller shaft 134 in substantially parallel to the ground, the final speed reducer 133 can be moved upward, and thus the suspension stroke could be improved. In the figure, the reference numeral 121 designates a vehicle body frame, the numeral 123 designates a saddle seat, the numeral 128 designates a suspension mechanism, and the numeral 129 designates a rear wheel.
FIG. 11 is a plan view showing the layout of the propeller shaft of the saddle riding type vehicle proposed above, in which the saddle riding type vehicle 120 was improved in the amount of movement of the wheels in the vertical direction by arranging a final speed reducer 133 at the center of the vehicle, and equalizing the lengths of the left and right drive shafts 135L, 135R. As a consequence, since the propeller shaft 134 had to be disposed diagonally, one each of the coupling for the side of the engine 122 and for the side of the final speed reducer 133, that is, two couplings 136, 137 in total were necessary.
In the saddle riding type vehicle 120 described above, the center of gravity was lowered and the suspension stroke was improved by disposing the propeller shaft in substantially parallel with the ground in side view and thus arranging the engine 122 at the lower position. However, it is desired to give further room for the suspension stroke to prevent limiting of the design or the layout.
In the saddle riding type vehicle 120 described above, the propeller shaft 134 is disposed by providing the couplings 136 and 137 on the side of the engine 122 and on the side of the final speed reducer 133 respectively. However, it is necessary to simplify the mechanism for transmitting power.